Benthic foraminifera as indicators of water renewal in Bertioga estuarine channel (SP, Brazil).

We use benthic foraminifera and hydrography as environmental indicators to characterize the estuarine channel of Bertioga (SP, Brazil). Salinity and temperature measured in four fixed stations (F1–F4) influence differentiation related to species habitat, fluvial discharge, and environmental quality. Tidal oscillation during neap and spring tides changes the Hansen and Rattray stratification-circulation classification from highly stratified (type 2b) to weakly stratified (type 2a). In the northern entrance close to Itapanhau River, F1 is highly stratified environment (type 2b), with significant difference between bottom and surface salinities, presenting Pararotalia sp., Pseudononion atlanticum, Hanzawaia boueana, and Quinqueloculina lamarckiana as indicator species. F2 in summer is highly stratified (type 2b) with large difference between surface and bottom salinity, whereas in winter is partially mixed weakly stratified (type 2a) with small difference between salinities and the agglutinated Arenoparella mexicana, Haplophragmoides wilberti, and Trochammina inflata thrives. In summer and winter, F3 is partially mixed weakly stratified (type 2a) with A. mexicana, H. wilberti, Trochammina inflata, Ammobaculites sp., and Ammotium salsum. In the southern entrance, F4 in the winter, is partially mixed, weakly stratified system (type 2a) that changes to highly stratified (type 2b) with large difference between salinities. This indicated low influence of fluvial freshwater and high influence of saline and polluted waters from Santos Channel where Arenoparella mexicana, Gaudryina exilis, and Ammotium cassis inhabits. Presence of Quinqueloculina spp. and Triloculina sp. indicates high saline influence, and presence of Ammonia tepida and Elphidium spp. indicates mixohaline environments which salinity dilution occurs.